Electroluminescent elements (organic electroluminescence elements) employing an organic thin film are being developed in recent years. Examples of methods for forming an organic thin film for use in an organic electroluminescence element include a vacuum deposition method and a wet film-forming method. The vacuum deposition method has an advantage that since superposition of layers by this method is easy, it is easy to improve charge injection from the anode and/or cathode or to confine excitons in the photosensitive layer. On the other hand, the wet film-forming method has advantages, for example, that no vacuum process is necessary and film formation in a larger area is easy, and that it is easy to incorporate a plurality of materials having various functions into one layer (coating fluid).
However, since superposition of layers by the wet film-forming method is difficult, elements produced using the wet film-forming method have lower driving stability than elements produced using the vacuum deposition method and have not reached a practical level at present except some of these. In particular, when organic thin films are superposed by the wet film-forming method, it is required to impart solubility in coating solvents to the material for organic electroluminescence elements by, for example, introducing a long-chain alkyl group thereinto. In the case where after the formation of an organic thin film, another organic thin film (upper layer) is formed thereon by the wet film-forming method, the material for organic electroluminescence elements which is contained in the lower layer is required to be insoluble in the coating solution for forming the upper layer. In a method which has hitherto been employed for such superposition of layers, a crosslinkable group or the like is introduced into the material for organic electroluminescence elements which is to be incorporated into the lower layer and, after formation of the lower layer, the crosslinkable group is crosslinked by a heat treatment, irradiation with energy, etc. to render the material insoluble in the coating solution for upper-layer formation. For example, non-patent document 1 and non-patent document 2 have proposed the following compounds having crosslinkable groups, and have proposed a method for superposing organic thin films in which an organic thin film becomes insoluble in organic solvents upon reaction of the crosslinkable groups.
